In certain applications it is necessary to provide a substantially acid-impervious metal substrate that comes into contact with another substrate whose chemical acidity acts to leach any available iron from the metal substrate. One important application is found in curing fixtures used to fabricate polymer composite resin-impregnated parts. In particular, resin-impregnated fiber of polymer composite material is placed on a steel curing fixture to give parts made therefrom a desired shape. The composite material is vacuum-bagged to the steel fixture and cured in an autoclave at an elevated temperature, all as known in the art. However, certain high-temperature polymer composite materials that cure above about 500.degree. F. will corrode the steel fixture while contemporaneously producing a bad part that exhibits undesirable reduced oxidative properties and high porosity.
It has been found that the reason for the above described corrosion and poor product yield is due to acid from the composite material acting to leach iron from the steel fixture. Because of the resulting untoward effect, it is most important to block acid passage into the fixture to thereby prevent iron leaching into the fabricated part. Accordingly, a primary object of the present invention is to provide methodology for providing a coating to a metal surface such as the surface of a steel curing fixture to thereby render that surface substantially acid impervious.
Another object of the present invention is to provide such methodology wherein the coating is deposited on the metal surface as a mixture of high-temperature resistant polymer particulate such as a polyamide particulate and a curable powder adhesive which thereafter is cured to adhere the polymer particulate as an acid impervious coating on the surface.
Yet another object of the present invention is to provide an acid impervious steel curing fixture having a high-temperature resistant polymer particulate coating thereon which is temperature resistant up to about 700.degree. F.
These and other objects of the present invention will be apparent throughout the description thereof which now follows.